It has heretofore been proposed to provide a process which makes it possible to obtain an oxygen enriched stream of gas suitable for those who need medical treatment. In some instances that process is used to provide a controlled atmosphere in an enclosed space such as an entire room in which the patient or patients may be seated. The known processes replace the use of pure bottled oxygen which is expensive and which requires extensive manipulation. Apparatus for carrying out the known processes, however, include several separate electrically operated valves, and the more valves used the more likely the system is to fail.
For nitrogen adsorption several molecular sieve adosrbents are known, including Type 5A. The molecular sieve adsorbent materials are packed into two cylindrical beds which are alternately used in a programmed cycle in which one bed is discharging an oxygen enriched primary effluent stream while the other bed is being purged of its adsorbed nitrogen by means including a diverted portion of the primary effluent stream. Such a process is disclosed in U.S. Pat. No. 3,280,536.
Silica gel is incorporated at the inlet of each bed to remove moisture that would reduce the nitrogen adsorbing capacity of the molecular sieve material.
Most of the conventional units do not utilize the compressor in a continuous cycle and therefore require either an air reservoir or a compressor unloader valve. Both of these expedients have the disadvantage that they are either bulky and expensive or noisy in operation.